In a wireless communication system that includes a plurality of base station devices, when communication areas (cells) set by the respective plurality of base station devices overlap each other, a signal transmitted by a base station device may arrive at a terminal device in a cell of neighboring another base station device, resulting in an interference signal for the terminal device.
It is well known that such interference can be suppressed by beam forming. That is, a base station device performs beam forming such that a beam is directed to a terminal device existing its own cell (also referred to as own terminal device, hereinafter) while a null beam is directed to a terminal device existing in a cell of another base station device (also referred to as another terminal device, hereinafter). Thereby, a signal (interference signal) from the base station device is less likely to arrive at the another terminal device, and thus interference is suppressed (refer to Non-Patent Literature 1 for beam forming).